Hello: My daughter does the same thing, as soon as daddy comes home she ignores mommy. It sure doesn't feel good but when Mommy has to work and daddy watches her, I'm all hers when I come home and she ignores daddy.
I'm not sure this is really caused by anything that your wife is doing. It may be true that your daughter sees you as the 'fun' parent and your wife as the law-giver, but I think it's quite common for children to go through a phase of very strong attachment to the opposite-sex parent. It's just very hard for the 'rejected' parent, particularly as she's the one who's spending all day with your child. My daughter did this and it went on for months. I found it very hard, but I knew deep down that she did really love me - she just found her Daddy more fun. Then she switched to me! (for a while anyway). We used to take turns putting her to bed each night and she would create merry hell if it was the turn of the "wrong' parent. My son went through a very long phase (about a year) of being attached to me, but my husband found that much easier to take than I had. As I say, it's hardest when you're the one spending all your time with the child and they don't seem to want you. This is a bit long-winded, but in short I don't think your wife is necessarily doing anything wrong. She may want to think about the attention she gives your daughter in the day, but if she feels fairly sure that she's getting it right (I know, who ever does?), she should just try not to worry and ride it out. It will pass.
Just to add to the other comments, my son did the same thing only it lasted maybe 2 years, right from when he was born his Dad was the only one to calm him etc. He'd scream when he left for work or went out the room. It was heartbreaking for me. When I was at home with him he'd ask me over and over where's Daddy? when's Daddy home? My husband didn't really help he lapped up the attention and I ended up feeling like a spare part!
It only seemed to change when I fell pregnant, all of a sudden he became Mummies boy. I don't know whether it was because I softened or was too tired to discipline but it gave my husband a shock! And we started dishing out the same amount of discipline and having equal play times. I don't know if was a phase or something I was doing or even something my husband was doing but its passed now.
Perhaps your daughter is sensing the arrival of a new baby and is clinging to you as a safety net. Hopefully it should even out when the baby is here, she's not going to have a choice who she goes to!
